The present invention relates to a mail relay method.
As electronic mails of mobile phones are becoming more popular, networks (called “carrier facility networks”) and a group of mail servers handle a lot of mail traffic, which are managed by a company (called a “mobile phone carrier”) providing a mobile phone communication service. Recently, attached files such as an image file and an audio file tend to increase the mail size, and it is expected that the traffic will increase more. Because of the background described above, a mobile phone carrier has problems of the mail server storage capacity and the network load.
There is a technology disclosed in JP-A-08-331173 as a method for reducing the mail server storage capacity and the network load. The technology disclosed in JP-A-08-331173 is as follows: the transmitting side, before sending an electronic mail, checks whether or not the receiving side can uncompress a compressed electronic mail, and, if the receiving side can do, sends the electronic mail including a compressed mail body.
The method described above attempts to solve the problem of an electronic mail system which transmits the electronic mail without compressing data as it is, that is, the problem that the communication cost is high and the communication line is congested in the case of a large amount of data.